1. Field of the Invention
The present invention relates to a brake system comprising a master cylinder that generates brake fluid pressure by a braking operation of a driver, and a slave cylinder that generates brake fluid pressure by a driving force of an electric motor that operates according to an electrical signal which is responsive to the braking operation by the driver.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2005-343366 discloses a brake system of the type referred to as a brake by wire (BBW) brake system, which converts a braking operation of a driver into an electrical signal used to operate an electric brake force generator or generating means, such as a motor cylinder, and operates a wheel cylinder by brake fluid pressure generated by the motor cylinder.
If a problem occurs that renders the electric motor inoperative when an electric brake force generator (slave cylinder) of the BBW brake system is generating brake fluid pressure to operate a wheel cylinder, a failsafe or failure backup process for braking is performed by supplying brake fluid pressure generated by a master cylinder to the wheel cylinder via the slave cylinder.
However, at the moment when the slave cylinder becomes unable to generate a driving force for pushing a piston, the piston is pushed back by brake fluid pressure within the wheel cylinder. Therefore, there is a problem that the brake fluid pressure within the wheel cylinder suddenly decreases until the brake fluid pressure supplied from the master cylinder is built up.